I am trying to implement a CRC16 in an arduino sketch. I got the crc.c file from online and I wanted to try it out. I created the other files to allow crc.c to run correctly. Here are my files.
crc.h:
#ifndef CRC_C_
#define CRC_C_
unsigned short crcsum(const unsigned char* message, unsigned long length, unsigned short crc);
int crcverify(const unsigned char* message, unsigned long length);
void crcappend(unsigned char* message, unsigned long length);
#endif // CRC_C_
crc.c:
/*
* Derived from CRC algorithm for JTAG ICE mkII, published in Atmel
* Appnote AVR067. Converted from C++ to C.
*/
#include "crc.h"
/* CRC16 Definitions */
static const unsigned short crc_table[256] = {
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};
/* CRC calculation macros */
#define CRC_INIT 0xFFFF
#define CRC(crcval,newchar) crcval = (crcval >> 8) ^ \
crc_table[(crcval ^ newchar) & 0x00ff]
unsigned short crcsum(const unsigned char* message, unsigned long length,
unsigned short crc)
{
unsigned long i;
for(i = 0; i < length; i++)
{
CRC(crc, message[i]);
}
return crc;
}
int crcverify(const unsigned char* message, unsigned long length)
{
/*
* Returns true if the last two bytes in a message is the crc of the
* preceding bytes.
*/
unsigned short expected;
expected = crcsum(message, length - 2, CRC_INIT);
return (expected & 0xff) == message[length - 2] &&
((expected >> 8) & 0xff) == message[length - 1];
}
void crcappend(unsigned char* message, unsigned long length)
{
unsigned long crc;
crc = crcsum(message, length, CRC_INIT);
message[length] = (unsigned char)(crc & 0xff);
message[length+1] = (unsigned char)((crc >> 8) & 0xff);
}
I call the function "crcsum" in the following file.
crc.ino:
#include "crc.h"
void setup() {
crcsum((const unsigned char*)"0123456789", 50000, 4);
}
void loop() {
// put your main code here, to run repeatedly:
}
The problem is that I get the following error.
crc.cpp.o: In function `setup':
/Users/SuperDuperBro/crc.ino:10: undefined reference to `crcsum(unsigned char const*, unsigned long, unsigned short)'
collect2: error: ld returned 1 exit status
Error compiling.
I know that my header file and functions are operating correctly because when I comment out the function call in crc.ino, everything compiles just fine.
Why am I getting this error? I have looked online and have been trying to fix it for a while, but I haven't had any luck. My guess is that the problem has to be something with the function parameters. I tried adjusting the parameters, but to no avail. Any input is greatly appreciated. Thank you all in advance!
Did you add crc.c into your arduino project?
Either wrap your include of crc.h with extern "C" or rename the crc.c into crc.ino:
The compiled function name would be different between C and C++.
crcsum(...)
name after C compiler would be just _crcsum. After c++ compiler the name would be something likecrcsum__Fcii
. extern "C" just tells compiler to expect these names to be in C format.